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Transcript
Biotic component Definitions Biological Communities and Species Interaction Organism Species Population Community Populations All members of a single species that live together in a specific geographic range Range from a small pond to a continent Communities All species living in a specified geographic region or all species that potentially interact with one another in a given region Ecosystems Communities of living things and their nonliving environment Small as a field Large as a half continent Have varied characteristics Variation Change over time, evolve Evolution Changes at the population level, organisms don’t evolve Survival of the fittest—producing the most offspring No direction Natural selection—interplay of organisms and environmental conditions Natural Selection Some have adaptations that allow them to survive Next generation will have greater frequency of those adaptations “In tune” with the environment as it exists at the present time Future is not known Critical Factors and Tolerance Levels Limits to what can be endured “comfort zone” Temperature Amount moisture and form—fog vs. rain (California redwoods) Seasonal variation—length, temp. extremes, etc. Soil types Range of tolerance Used to be big thing—id limiting factors Tolerance Gradient or continuum Optimum range—species do best, most numerous Range (or zone) of stress—can exist, but smaller population size Range of intolerance (or zone)—species are absent Remember—in each population, variation exists Tolerance Keystone Species Species or group of species with impacts larger than by mere abundance Usually considered to be top predator May be less conspicuous Keystone Species Fungi: recycle, mineral mobilization and absorption Kelp: provides food, shelter, structure Sea otter: eat shellfish, hunted, no shellfish predation Figure 6.12a Figure 6.12b Foundation Species Play major role in shaping communities by creating or enhancing habitat that benefits other species Elephants: knock over trees Birds: distribute seed Mosses: breakdown rock Prairie dogs: prevent soil compaction Environmental Indicators Species that are indicators of certain, relatively specific, environmental conditions If you see species X, then you know that:………. If you see alpine lotus, then you know that you are above tree level, precipitation is snow, etc. Indicator Species Tied to specific biotic communities or Success ional stage (lodgepole pines), or Environmental condition Certain plants found only salt marshes Alpine plants only above tree line Umbrella species Require large blocks of relatively undisturbed territory to maintain viable populations Consequence—other species are maintained or saved Caribou or other migratory animals—not isolated large areas (islands) but large areas connected by “migratory freeways” People react to emotionally “Bambi” effect “Shamu” Increase public awareness Productivity Diversity Complexity Resilience Stability Structure Rate of biomass production Flagship Species Community Properties Productivity Biodiversity Measure of number of species niches genetic variation Complexity Number of species at each trophic level Number of trophic levels in a community Tropical rainforests Resilience and Stability Tendency to remain stable and constant over time Constancy Inertia Renewal Biodiversity Complexity of species composition 3 factors determine richness (or lack of it) Variety of species (we tend to decrease biodiversity) So. Cal.: problems with Caulerpa used in hobby aquaria, dumped into ocean, takes over Sparrows: “Aggressive” cavity nesters Biodiversity Species distribution and population size—geographic Development in So. Cal.: loss of wetlands and desert oases Genetic variety (gmo): food and ornamental crops Habitat Types of Interaction Address Physical surroundings Niche Mode of living and resource acquisition occupation Niche Fundamental Niche--full range of resources that could be exploited if no competition Realized Niche—resources that are actually exploited Figure 6.2a Figure 6.2b Ways to Exploit Generalists—cockroaches, opossums, humans (?)—wide range of niches Specialists—pandas—narrow range Entrepreneurs—elephants, chimps, humans (?)—learn new ways in new situations Competition Seen in species (closely related) occupying niches that overlap to some degree Long term competition between species with same niche is rare Competition Usually results in elimination of one—extinction, migration, change behavior, etc Problem with introduced species—alien and invasive--kudzu, tumbleweed, rats, cats Resource Partitioning and Niche Specialization Resource Partitioning Share habitat—exploit resources in slightly different ways Temporal Location Creosote bush in Southern California deserts Figure 6.3 Resource Exploitation Predation—one freestanding organism feeding on parts or all of a second organism (prey) Complex relationships Populations are linked Cyclical change in abundance or decline of populations, populations held in check Figure 6.4 Resource Exploitation Parasitism—type of predation Predator feeds on prey but does not immediately kill it Complex life cycles One host, different tissues--Dracuncula Different hosts at stages of life cycle—malarial parasite Figure 6.7 Resource Exploitation Most efficient parasites don’t kill off With time, effect on predator may not be as severe Predator and prey develop mechanisms to “deal” with each other Toxins (salamanders and garter snakes) Coevolution Resource Partitioning Culling of less capable “weaker” members of population Adaptive “arms race” Promotes species diversity Frees up space Competition Resource Exploitation Intraspecific—among members of same species Intense—same resource requirements Jackals fighting over carcasses Resource Exploitation Seedlings and light in forests Production of toxins to prevent germination Territoriality Different life stage, different foods Immature caterpillar—eats leaves, adult butterfly sucks nectar Interspecific Resource Exploitation Different species Seed production Avoidance Mimicry—avoid predation Adaptations to predator-prey relationships Batesian—one species copies the form of another to gain superior protective capability— syrphid fly and bees Mullerian—several species that have protection against predators come to resemble one another, collectively provides a “learning” experience—fewer individuals are killed Adaptations to predator-prey relationships Commensalism: interaction that does not harm either partner and may be beneficial to one, Finding Nemo—clownfish and anemones Mutualism-both partners benefit—fungi and roots—orchids can’t live without fungi on and in their roots, remora and sharks Mutualism Coevolution—interdependent evolution Extensive in flowering plants and insects Orchids and wasps Yucca and moths UV only landing patterns on certain flowers Community Properties Primary productivity—biomass production Abundance—total number of organisms Diversity—measure of the different species Many variations—dependent on all components of the area being discussed Such as…. Community Properties Complexity—number of species at each trophic level and the number of tophic levels Connectedness—lots of trophic levels with lots of interactions within in a trophic level and between trophic levels Few straight lines—a complex food web Resilience and Stability Some communities appear to remain stable for a long time Constancy—lack of fluctuation Inertia—resistance to change Renewal—ability to repair after change Stability Rule of thumb—more diverse, more resilient If one species is lost, another one there Removal of keystone species may destroy the community—destruction of certain trees and removal of dead trees has decimated western bluebird Community Properties Edge effect—boundary between one community and its neighbor(s) Dramatic or gradual--forest bordering prairie or grassland into sagebrush Ecotones—boundaries between adjacent communities Ecotones Open community—gradual or indistinct boundaries Closed community—sharply divided from neighbors Edges may be shallow—grazed vs. ungrazed land or deep—forest edge with blowdown, erosion, etc Succession Change in a community—water availability, soil deposition, change of plants Primary succession—sequence that occurs on previously unoccupied land Secondary succession—sequence occurs when existing community is altered by human activities or natural occurrences Primary Succession Starting state—little or no life, exposed rock, mud, ash (Mt. St. Helens) 1-windborne plants 2-increase in biomass (stops, may reverse in time 3-longer-lived plants more prevalent than ephemerals Primary Succession (cont’d) 4-increased species diversity 5-facilitation of growth for later species through action of preceding species—break down soil, build up soil layers, provide habitat 6-late arriving species drive out earlier species—compete for sunlight, soil, etc Secondary Succession Occurs when existing community is disrupted, natural or human activity Occurs when habitat is left alone following a major disturbance of original final-state community—woods that grow into abandoned farm fields Climax Community Stable end product of any process of succession May be shifts inn some animal and plant components but grassland stay grassland Post climax community-lodgepole pine forests appear to die off, what follows Disclimax—adapted to cycle of destruction and regeneration—fires in Western US, Southern California chapparal Increasing Problems Alien and invasive species—plant and animal Discontinuous tracts of land